1. Field of the Invention
The present invention relates to a sensor fault detection circuit, a relative angle detection device, and an electric power steering apparatus.
2. Description of Related Art
In the related art, there is proposed a technology in which an electric power steering apparatus includes a torque sensor (relative angle detection device), and an electric motor is controlled based on a detection value from the torque sensor.
For example, a torque sensor disclosed in JP-A-2009-255645 has the following configuration. That is, the torque sensor is configured to include a torsion bar that coaxially connects an input shaft to an output shaft; a ring-shaped magnet attached to an end portion of the input shaft; a pair of magnetic yokes attached to an end portion of the output shaft; a magnetic sensor that detects magnetic flux density occurring in the magnetic yokes; and the like.
A relative angle detection device disclosed in JP-A-2013-213677 has the following configuration. That is, the relative angle detection device includes first output means for outputting a signal which corresponds to a relative rotation angle between two rotation shafts which are coaxially disposed; a first amplifier circuit that is configured as a combination of circuits operating reversely to each other, and amplifies the output signal from the first output means; a second output unit that outputs a signal that corresponds to the relative rotation angle, and has a characteristic which is contradictory to that from the first output means; a second amplifier circuit that is configured as a combination of circuits operating reversely to each other, and amplifies the output signal from the second output unit; a first resistor between the first amplifier circuit and a power supply terminal that receives a power supply voltage, or between the first amplifier circuit and a reference terminal that receives a reference voltage; and a second resistor that is provided between the second amplifier circuit and a power supply terminal that receives a power supply voltage, or between the second amplifier circuit and the reference terminal that receives a reference voltage, and in a portion equivalent to a portion in which the first resistor is provided.